This invention relates generally to aircraft systems and, more specifically, to aircraft braking systems.
After takeoff, the landing gear of an aircraft is retracted as soon as possible. In order to safely stow the landing gear in the fuselage, the wheel speed must be zero (not spinning). Otherwise, damage can occur to components, such as hydraulic lines, within the landing gear bay. This is of special concern when a spinning wheel has shredded. For example, tread rotating with a failed tire can potentially damage flight equipment when the rotating, failed tire enters the wheel well.
Presently wheel braking during landing gear retraction is a passive non-monitored function. That is, the flight crew has no way of knowing if the wheels are spinning while being retracted. Thus, the flight crew does not have the ability to stop gear retraction if the wheels are spinning. Therefore, there exists a need to ensure that wheels are not spinning before the landing gear is fully retracted.
The present invention is a method and system for braking aircraft landing gear wheels after initialization of landing gear retraction. The system takes advantage of existing physical components of a brake control system. Thus very little new hardware needs to be added to accomplish the functionality of the present invention. The present invention is an active control system. The Brake Metering Valves in an airplane can be made xe2x80x9cless costlyxe2x80x9d, xe2x80x9cless complexxe2x80x9d and xe2x80x9clighterxe2x80x9d by elimination of the existing gear retract function. Gear retraction is made xe2x80x9cmore safexe2x80x9d because the threat from a flailing tire tread is greatly reduced. The braking system formed in accordance with the present invention reliably stops tire rotation before a failed tire can enter the wheel well where a tread rotating with the tire can potentially damage combinations of flight critical equipment.
An embodiment of the system includes monitors, controlling components, measurement components, a fault recording memory, fault annunciation components, wheel braking system and brakes. The monitors monitor speed of the landing gear wheels and landing gear position. The control component generates braking instructions based on the monitored speed of the wheels and position of the landing gear. The measurement components provide indications proportional to wheel speed and landing gear position. The fault recording memory records incidents of wheels spinning above a threshold when the landing gear position is at a given threshold. The braking system component applies brake pressure according to the generated braking instructions.
The generated braking instructions suitably include instructions to implement wheel braking with onset of gear retraction, increase braking if the landing gear position is at least to a threshold position and wheel speed is greater than a speed threshold value.
The system also includes a component for alerting the flight crew, if the landing gear position is at least to a threshold position and wheel speed is greater than a speed threshold value.
The system includes a component for inhibiting landing gear retraction, if the landing gear position is at least to a threshold position and wheel speed is greater than a speed threshold value.